The overall objective is to define the chemical and physical parameters which regulate immune cellular recognition. We have obtained plasma membrane vesicles obtained from tumor target cells and are characterizing them for enzyme activities, extent of glycosylation of H-2 proteins, asymmetric orientation, and interaction with specific alloantibodies. We further plan to purify the histocompatibility antigens by isoelectric focusing and reconstitute them into defined lipid systems which mimic the environment of the naturally occurring lipids in the plasma membrane. We will test these reconstituted antigens for the ability to inhibit recognition between a specific cytotoxic T cells and its target cell or to inhibit target cell killing.